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Configuring IP Multicast Routing
Configuring Optional IGMP Features
All systems on the subnet must support the same version. The switch does not automatically detect Version 1 systems
and switch to Version 1. You can mix Version 1 and Version 2 hosts on the subnet because Version 2 routers or switches
always work correctly with IGMPv1 hosts.
Configure the switch for Version 1 if your hosts do not support Version 2.
This procedure is optional.
BEFORE YOU BEGIN
Review the Information About IGMP, page 676.
DETAILED STEPS
To return to the default setting, use the no ip igmp version interface configuration command.
EXAMPLE
The following example configures the router to use IGMP Version 2:
ip igmp version 2
Modifying the IGMP Host-Query Message Interval
The switch periodically sends IGMP host-query messages to discover which multicast groups are present on attached
networks. These messages are sent to the all-hosts multicast group (224.0.0.1) with a time-to-live (TTL) of 1. The switch
sends host-query messages to refresh its knowledge of memberships present on the network. If, after some number of
queries, the software discovers that no local hosts are members of a multicast group, the software stops forwarding
multicast packets to the local network from remote origins for that group and sends a prune message upstream toward
the source.
The switch elects a PIM designated router (DR) for the LAN (subnet). The DR is the router or multilayer switch with the
highest IP address for IGMPv2. For IGMPv1, the DR is elected according to the multicast routing protocol that runs on
the LAN. The designated router is responsible for sending IGMP host-query messages to all hosts on the LAN. In sparse
mode, the designated router also sends PIM register and PIM join messages toward the RP router.
This procedure is optional.
Command Purpose
1. configure terminal Enter global configuration mode.
2. interface interface-id Specify the interface to be configured, and enter interface
configuration mode.
3. no shutdown Enable the port, if necessary. By default, UNIs and ENIs are
disabled, and NNIs are enabled.
4. ip igmp version {1 | 2} Specify the IGMP version that the switch uses.
Note: If you change to Version 1, you cannot configure the ip
igmp query-interval or the ip igmp
query-max-response-time interface configuration
commands.
5. end Return to privileged EXEC mode.
6. show ip igmp interface [interface-id] Verify your entries.
7. copy running-config startup-config (Optional) Save your entries in the configuration file.
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